Relaxation oscillator based keypad decoder

Details Relaxation oscillator based keypad decoder Relaxation oscillator based keypad decoder

2006-06-20

2006-06-20

Wong, Albert K. (Department: 2612)

Coded data generation or conversion

Bodily actuated code generator

Including keyboard or keypad

C341S022000, C345S169000, C327S115000

Reexamination Certificate

active

07064682

ABSTRACT:
The keypad interface element of this invention uses a relaxation oscillator and a digital keypad processor having a counter/timer to decode specific keys. The RC portion of the relaxation oscillator includes a resistance ladder and a set of momentary on pushbutton switches disposed change resistance dependent upon which key is pressed. This causes the relaxation oscillator to produce an output signal having a corresponding frequency. The counter/timer of the digital keypad processor produces a count corresponding to the oscillator frequency. The digital keypad processor latches and holds a binary number specifically identifying the depressed key. A state machine in the digital keypad processor provides transient-free, noise immune keypad decoding.

REFERENCES:
patent: 6184805 (2001-02-01), Uggmark
patent: 6222466 (2001-04-01), Uggmark

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